Rajkamal Mohanram's Blog

Potpourri of Stuff!

Blackholes – They aren’t really that black!

English: Black hole jet diagram. http://www.na...

English: Black hole jet diagram. http://www.nasa.gov/centers/goddard/images/content/96552main_jet_schematic.jpe (Photo credit: Wikipedia)

All of us would have come across the term “black hole”. What is it? Why is it even named that way. I’ve been reading a book by Stephen Hawking – “A brief history of time – From the big bang to black holes”.

For those who don’t know, Stephen Hawking is one of the greatest minds in astrophysics. He, unfortunately, is confined to a wheel chair because he is physically challenged but his mind wanders into the realms of outer space.Being born on Galileo’s death anniversary,  he holds the position of Sir Issac Newton as a Lucasian Professor of Mathematics.

“Supernova” – The Black hole’s big angry brother

Black holes are hypothetical objects. They are thought to be the result of the death of a star that is approximately above three times the mass of our sun. I’ve been studying these concepts for a while so from what I know, the death of our sun would be a tragic and a violent one. Our sun, in approximately 5 million years from now (I’m contended that we need not worry of being cooked to a cinder), will blow up like a huge balloon. Since the hydrogen is getting used up and by that time, all the hydrogen would have been exhausted. So, the burning of Hydrogen stops and instead, it starts burning helium. The diameter of the sun would be 100 times the radius of earth (as opposed to the current diameter of 10 times earth’s). There would be very less energy compared to the energy that we have now but there will be much more surface area. This keeps happening and all of a sudden, the sun explodes! Boom! A supernova. Unless the human race has made it to some outer part of the solar system (Like Saturn’s moon – Titan), this will mark the extinction of the race. Earth, along with the other inner planets will be burnt beyond recognition. The remnants of this supernova will be visible for a long long time.

Okay.So? How is a black hole even remotely connected to the crap told above?

Well, that’s where we are getting now. If the star happens to be in “a bad diet” and it is huge with a lot of mass – A mass greater than the Chandrasekhar limit, then, the star at it’s “deathbed” is unstable and cannot stand it’s own gravity( unlike the sun which was stable all along but exploded due to the burning of helium and the “cooling” effect). The star collapses into it’s own gravity and Voila! We have a black hole. Now, the black hole is a “gravity field” that sucks anything that passes close by. Be it a hydrogen atom, an asteroid and what not. Even a beam of light cannot escape it’s vicious pull. Now, the objects captured by this black hole are thought to take up a spiral path around the black hole.

There is an “event horizon” which is like a barrier that prevents us from looking at the events that occur inside it. That is, to an observer outside, the events inside the horizon are nothing but the weirdest mystery – It is next to impossible to detect what is going on inside the horizon from outside. Similarly, once the observer is inside, he is disconnected completely from the events that are occurring outside the horizon. Also, the events or any action that happens inside the event horizon cannot affect the objects or events outside the horizon and vice-verse. This, sadly, breaks all the laws of physics. So, if Newton were sitting below an apple tree inside the horizon, the apple might not have fallen down or even if it had, it might not mean anything to us because we are outside the event horizon and their laws of the universe would differ from ours.

Hypothetically, if we imagine an observer making it into the event horizon of the black hole, he’d be dead meat. At the center of the black hole lies a singularity, an infinite curvature of space and time. No object can enter or exit the singularity. The observer will be torn into pieces by the pull of gravity, he will be reduced to molecules, molecules into atoms, the electrons would be kicked out of the atoms, the atoms will be shredded into separate sub-atomic particles and at last, the sub-atomic particles will be ripped apart into quarks. Nothing else passes into the singularity.

As the name suggests, the black holes are completely invisible unless they are neighboring a star. If the black hole is near a star, then, it “eats” the star as long as it can, for millions and millions of years until all the fuel in the star is over. Then, it becomes invisible again after the star has been thoroughly consumed.

The nearest black hole to the earth is called Cygnus X1. It is ~ 10,000 light years away from earth. You might have been wondering what if a black hole swallows our planet, or even the entire solar system. Yea, you are right, it can happen! But the black hole needs to be at a distance of at least 10 light years to have significant effect on the earth or the other planets. The swallowing of the earth, sun or other planets in the solar system is strictly science fiction.

The black holes are still being extensively studied by scientists. They are remote, weird and scary. Super massive black holes are formed as a result of the “self-swallowing” or self-collapsing of a star that has way to much mass than our sun. The Milkiway galaxy is known to harbor gigantic super massive black hole at it’s center.

The links in the post might help you to understand the concept better. Follow the links to wiki and YouTube.

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